Light modulator with a light-absorbing layer

ABSTRACT

A spatial light modulator includes a first region and a second region. A light-absorbing layer contacts at least a portion of the second region. The light absorbing layer includes a first layer and a second layer, the second layer having a reflectivity less than about 75%.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of currently pending U.S. patentapplication Ser. No. 10/903,032, filed Jul. 30, 2004, which isincorporated herein by reference in its entirety.

BACKGROUND

Various technologies have been proposed for projection and displaysystems such as those utilizing spatial light modulation employingvarious materials. Among these are micromechanical spatial lightmodulation (SLM) devices in which a large portion of the device isoptically active. In such systems a pixel area includes usable area forcolor generation for the imaging system. However, these systems alsohave areas that are not available for light generation, but that doreflect light that may, in some instances, degrade the color gamut andthe contrast of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, features, and advantages will become apparent by reference tothe following detailed description drawings in which like referencenumerals correspond to similar, though not necessarily identical,components. For the sake of brevity, reference numerals having apreviously described function may not necessarily be described inconnection with the subsequent drawings in which they appear.

FIG. 1 is a top view of an embodiment of a representative pixel cell ofa light modulation device;

FIG. 2A is a cross-sectional view taken along the 2-2 line of FIG. 1showing the representative pixel cell with a light-absorbing layerpositioned on a second region according to an example embodiment;

FIG. 2B is an enlarged cross-sectional view of the light-absorbing layerof FIG. 2A according to an example embodiment;

FIG. 2C is an enlarged cross-sectional view of the light-absorbing layerof FIG. 2A according to an example embodiment;

FIG. 3 is a top view of an embodiment of part of a light modulationdevice showing a light-absorbing layer over the second region(s)according to an example embodiment;

FIG. 4 is a cross-sectional view of a representative pixel cell of adual gap display device showing the light-absorbing layer deposited on apassivation layer according to an example embodiment;

FIG. 5A is a cross-sectional view of a representative pixel cell of asingle gap display device showing a sacrificial layer deposited thereonaccording to an example embodiment;

FIG. 5B is a cross-sectional view of the embodiment of FIG. 5A with aportion of the sacrificial layer removed according to an exampleembodiment;

FIG. 5C is a cross-sectional view of the embodiment of FIG. 5B with anabsorbing layer established thereon according to an example embodiment;

FIG. 5D is a cross-sectional view of an embodiment of FIG. 5C with thesacrificial layer removed;

FIG. 6 is a schematic view of a display device utilizing thelight-absorbing layer as depicted in FIG. 2B according to an exampleembodiment; and

FIG. 7 is a graph depicting the optical reflectance of variousembodiments of the light-absorbing layer.

DETAILED DESCRIPTION

Disclosed herein is a light-absorbing layer construction suitable foruse with various electronic devices such as optical electronic displaydevices, for example spatial light modulators and the like. Withoutbeing bound to any theory, in some embodiments, the light-absorbinglayer may reduce reflection of incidental light from the areas notavailable for color generation, and allow most of the reflected light tobe dominated by the pixel area of the device in which it is used.

In an example embodiment as disclosed herein, a light-absorbing layer(hiding layer, or HID layer) is deposited over regions of the lightmodulation device that are not available for usable light generation(referred to herein as the second region). These regions may beancillary members of the light modulation device that support andconnect the operative areas together or may be artifacts remaining fromthe fabrication process. Generally, light that reflects from theseregions may degrade the color gamut and the contrast of the associatedsystem. The light-absorbing layer may advantageously substantiallyprevent light from reaching the regions of the light modulation devicethat are not available for usable light generation. The light-absorbinglayer may also advantageously result in reduction in the dark-statereflected light and an increase in the usable light for colorgeneration.

Pursuant to some example embodiments, the light-absorbing layer mayinclude at least one layer containing at least one material capable ofabsorbing at least a portion of directed light having a wavelength in asuitable predetermined range. One non-limiting example of apredetermined range is the range of visible light, i.e., 400 to 700nanometers. Suitable materials include, but are not limited to at leastone of tantalum aluminum alloys, tungsten silicon nitride alloys,tantalum nitride alloys, nickel, nickel alloys, titanium nitride alloys,and mixtures thereof.

The light-absorbing layer may be employed with various light modulationdevices of which spatial light modulation devices are a non-limitingexample. Suitable devices will generally include a substrate, a firstregion disposed on a first portion of the substrate, and a second regiondisposed on a second portion of the substrate. As used herein the term“first region” is defined as a region or regions of the associateddevice that is generally usable for color generation. Various hues ofcolor may be used in suitable display systems in which pixel cellshaving first region(s) are employed. The term “second region” as usedherein is defined as a region or regions located on, in and/or adjacentthe substrate that is/are not available for primary purpose or function(e.g. color generation) but possesses a degree of reflectivity. Examplesof second regions include, but are not limited to, architecturalelements to support function of the device, as well as artifactsremaining from fabrication or assembly. Examples of functionalarchitectural elements include, but are not limited to, flexures, posts,bottom capacitor plate regions, boundary regions, and the like.Non-limiting examples of fabrication artifacts include vias, clearoutapertures, and the like.

For illustrative purposes, FIG. 1 depicts a portion of a lightmodulation device, or a pixel cell 10. The pixel cell 10 has a pixel 12.As employed herein, the pixel 12 is the area of the pixel cell 10 thatactively modulates light in various colors. Modulation may beaccomplished in any suitable manner. It is contemplated that the activeor functional portion of each pixel cell 10 constitutes a primary lightreflective region 14.

The pixel 12 is depicted as an essentially square member in FIG. 1.However, it is contemplated that pixel 12 may have any suitable geometryand/or configuration. Further, it is to be understood that an array ofpixels 12 may be used. The array may include any number of pixels 12 toachieve the desired function. For simplicity, the discussion will bedirected to a single pixel 12 as shown in FIG. 1.

In addition to the first region 14, the pixel cell 10 shown in FIG. 1has other areas or regions that are not available for active lightmodulation. These regions may be necessary for ancillary functions ofthe pixel cell 10 or may be artifacts remaining from fabrication.Generally, light reflected from these areas during pixel operation inits dark state may, in some instances, degrade the color gamut and thecontrast of the associated system. As depicted in FIG. 1, these areasare collectively designated as second region 16. Non-limiting examplesof elements that may be included in the second region 16 of a pixel cell10 include, but are not limited to post(s) 18, bottom capacitor plateregion(s) 20, clearout holes or region(s) 22 and flexure(s) 24, andboundary regions 27. It is to be understood that the configuration,location, and operation of various elements in the second region 16 mayvary from pixel cell 10 configuration to pixel cell 10 configuration. Itis contemplated that architectural features included in the secondregion 16 may be shared by one or more pixel cells 10 in a given arrayas desired and/or required. Thus, posts 18 may be shared with adjacentpixel cells 10. Similarly, flexures 24 may also be shared as desired.

Each pixel 12 may include a suitable architecture such as support post18. The support post 18 may be positioned as desired to facilitateoperation of the device. As depicted, the support posts 18 may bepositioned proximate to locations such as edge 25 depending upon thespecific architecture of the pixel cell 10. Similarly, each pixel 12 mayinclude various other incidental light reflective structures atlocations suitable for pixel 12 function fabrication or the like.Individually or collectively, these elements form the second region 16.It is contemplated that the second region 16 may make up a contiguous ornoncontiguous region on the pixel cell 10.

A light-absorbing layer 28 (shown in FIGS. 2A and 2B) contacts at leasta portion of the second region 16 in a manner that reduces the amount oflight reflected from the region 16. The terms “contacts,” “contacting,”“in contact with,” or the like as used herein is contemplated asincluding direct contact and/or indirect contact between two or moreelements. It is contemplated that light-absorbing layer 28 may contactportions of the second region 16 sufficient to reduce undesiredreflected light without undue compromise to the function of the firstregion 14. Thus, the light-absorbing layer 28 may contact all orselected portions of the second region 16.

It is to be understood that the light-absorbing layer 28 may cover thesecond region 16 in any suitable manner that permits overlyingrelationship of the light-absorbing layer 28 with the second region 16.This may include direct contact between the respective elements and/orstand-off (i.e. indirect contact) between the elements as desired.

To further illustrate the light-absorbing layer 28 disclosed herein,attention is directed to FIGS. 2A, 2B, and 2C. FIG. 2A is across-sectional view taken of a portion of the pixel cell 10 taken alongthe 2-2 line of FIG. 1 that includes portions of the first region 14 andthe second region 16 with the light-absorbing layer 28 contacting thesecond region 16. FIGS. 2B and 2C are enlarged cross-sectional views ofembodiments of light-absorbing layer 28.

Now referring specifically to FIG. 2A, pixel cell 10 includes asubstrate 26 composed of a suitable material. Examples of suitablesubstrate materials include, but are not limited to, silicon, glass,plastics, and various materials that can support CMOS architectures aswell as other architectures and configurations.

The first region 14 may be composed of suitable reflective andmodulating layers. As depicted herein, the first region 14 may include alower reflective layer 15 and an overlying practical reflective layer 17with an air gap 19 defined therebetween. A non-limiting example of onetype of configuration is found in Fabry-Perot devices and the like.Other configurations having light reflective regions, such asmicromirrors, liquid crystal on silicon (LCOS), and liquid crystaldisplays (LCD), are also contemplated.

At least one second region 16 is also disposed on substrate 26. Asmentioned hereinabove, the “second region” is any region present in thepixel cell 10 that is not available for light modulation. Reflectionsemanating from the second region 16 may result in the degradation of thecolor gamut and the contrast during operation of the light modulation ordisplay system employing such pixel cell(s) 10. It is contemplated thatsecond region 16 may be composed of contiguous region(s) of pixelarchitecture. It is also possible that various noncontiguous regions maybe disposed on the surface of substrate 26. The second region 16 mayinclude various architectural features associated with the pixel cell10.

In an embodiment, the light-absorbing layer 28 contacts at least aportion of the second region 16. As depicted in FIG. 2A, anon-limitative example of the light-absorbing layer 28 is contacting thesecond region 16 in a manner that defines a gap 29 located between theupper face of the second region 16 and the lower face of thelight-absorbing layer 28. The light-absorbing layer 28 may be mounted onsuitable supports (not shown) to define and maintain the appropriate gap29.

In some embodiments, the light-absorbing layer 28 may directly contactthe second region 16. It is also contemplated that various intermediatelayers (not shown) may be interposed between the second region 16 andthe light-absorbing layer 28. As such, where the light-absorbing layer28 is referred to as being “on” or “at” the second region 16, this meansthat the layer 28 contacts the region 16 either directly or via one ofthe intermediate layers.

It is to be understood that the light-absorbing layer 28 may include atleast two layers connected to one another. Where the various layers ofthe light-absorbing layer 28 are referred to as being “connected to” or“disposed on” other layers of the light-absorbing layer 28, as usedherein, it is contemplated that this includes layers in direct contactwith each other, or layers having other layers interposed therebetween.As depicted in FIG. 2B, the first (e.g. reflective) layer 40 ispositioned proximate to the second region 16 and the second layer 42 ispositioned distal to the second region 16.

It is contemplated that at least one of these two layers 40, 42 iscomposed of a material that reflects at least a portion of directedlight at a given wavelength range, such as 400 to 700 nanometers.Suitable materials include, but are not limited to at least one oftantalum aluminum alloys, tungsten silicon nitride alloys, tantalumnitride alloys, nickel, nickel alloys, titanium nitride alloys, andmixtures thereof. Suitable tantalum aluminum alloys are generallydepicted by the formula Ta_(x)Al_(y) in which x and y may be present ata ratio between about 1:1 and about 1:2, tantalum to aluminumrespectively. Suitable tungsten silicon nitride alloys are generallydepicted by the formula WSiN in which the various components aregenerally present in atomic ratios ranging between about 2:4:5 and2:4:9. Similarly titanium nitride may be depicted by the formulaTi_(x)N_(y) with x and y representing an atomic ratio ranging betweenabout 3:4 and about 4:3. In the embodiment depicted herein, the secondlayer 42 disposed distal to the second region 16 is composed of theenumerated materials, while the first layer 40 is composed of a materialhaving reflectivity over a broader spectrum, including, but not limitedto, aluminum, aluminum alloys, silver, silver alloys, gold, gold alloys,tantalum aluminum, titanium nitride, tungsten silicon nitride, tungsten,silicon, chromium, copper, and mixtures thereof.

As depicted in FIG. 2B, the light-absorbing layer 28 may includeadditional (e.g. three, four, etc. . . . ) layers. In a three layerconfiguration, the light-absorbing layer 28 includes a first layer 40, asecond layer 42 connected to the first layer 40, and a third or standofflayer 44 interposed between the first layer 40 and the second layer 42.Generally, the combination of these three layers 40, 42, 44 is utilizedto advantageously absorb light that would otherwise reflect off of thesecond region 16 and degrade the color gamut and contrast of theassociated system. In an embodiment, a fourth (e.g. transparentdielectric) layer 45 may be disposed on the second layer 42.

It is to be understood that the thicknesses of each of the first layer40, the second layer 42, the third (standoff) layer 44, and the fourthlayer 45 may be sufficient to reduce the percentage of visible lightreflected from the second region 16. The light-absorbing layer 28 isconfigured to absorb at least a portion of the light directed to thesecond region 16 in the visible light region. More particularly, therespective thicknesses of layers 40, 42, 44 and 45 may be configured toabsorb at least a portion of directed light having a wavelength rangingbetween about 400 nanometers and about 700 nanometers. It iscontemplated that materials used for the first layer 40, the secondlayer 42, the third layer 44, and the fourth layer 45, respectively, maybe tuned at the visible spectrum to absorb incidental reflected light.

The first layer 40 of the light-absorbing layer 28 may be made of anysuitable material having a reasonably high reflectivity. In anembodiment, the first layer 40 has a reflectivity greater than about 75%(e.g. a reflector layer). It is contemplated that materials having areflectivity greater than about 85% may be advantageously employed, withsome materials of choice typically having a reflectivity greater thanabout 90%. Examples of suitable materials that may be employed in thisembodiment of first layer 40 include, but are not limited to at leastone of aluminum, aluminum alloys, silver, silver alloys, copper, and/orgold. In an alternate embodiment, the reflectivity of the first layer 40may be lower than about 75%. Suitable materials for the first layer 40of this embodiment include, but are not limited to tantalum aluminum,titanium nitride, tungsten silicon nitride, tungsten, silicon, chromium,and mixtures thereof. The first layer 40 may have any suitable thicknessappropriate for achieving the desired reflectivity and overallperformance of the light-absorbing layer 28 and associated pixel cell10. It is contemplated that the first layer 40 may have a thicknessranging between about 300 angstroms and about 5,000 angstroms.

The first layer 40 may exhibit substantially little or no transmittance.Therefore, in an embodiment, additional layers (a non-limitative exampleof which may be optically non-functional layers) may contact a side ofthe first layer 40 that is opposed to the side that contacts the secondor third layers 42, 44 (i.e. under the first layer 40). It is to beunderstood that these additional layer(s) may not substantiallyinterfere with the function of the light-absorbing layer 28. Withoutbeing bound to any theory, it is believed that the first layer 40 of thelight-absorbing layer 28 may not substantially transmit light through tothe additional layers, and thus the structure could be adapted in thismanner without substantial change in the functionality of thelight-absorbing layer 28.

The second layer 42 of the light-absorbing layer 28 may include anysuitable material capable of absorbing at least a portion of reflectedlight in a range between 400 and 700 nanometers. In an embodiment asdepicted, the second layer 42 materials include, but not limited to atleast one of tantalum aluminum alloys, tungsten silicon nitride,tantalum nitride, nickel, nickel alloys, titanium nitride, and/ormixtures thereof. In a non-limitative example, the second layer 42includes tantalum aluminum. The second layer 42 may be constructed withany thickness suitable to facilitate light absorption in the desiredrange and to facilitate the overall performance of the light-absorbinglayer 28 and the associated pixel cell 10. In one embodiment, it iscontemplated that the thickness of the second layer 42 ranges betweenabout 50 angstroms and about 300 angstroms. Without being bound to anytheory, it is believed that, in some embodiments, varying the thicknessof the second layer 42 may assist in tuning the second layer 42 in thevisible spectrum with absorption of at least a portion of reflectedlight having a wavelength between 400 and 700 nanometers occurring.Thus, for example, a material such as a tantalum aluminum alloy exhibitsa broad low absorptivity band when present in thicknesses less thanabout 100 angstroms. Therefore, a tantalum aluminum alloy may beestablished as the second layer 42 in the light-absorbing layer 28 topermit light absorption in the visible spectrum to be tuned to thedesired wavelength region.

A third (standoff) layer 44 may be interposed or established between thefirst layer 40 and the second layer 42. The third layer 44 has athickness T and a degree of optical transparency value such that aportion of light directed at the second region 16 is absorbed. Asdepicted, the third layer 44 may serve to form an optical path lengthdifferential between light reflected off of the first layer 40 and lightreflected off of the second layer 42 facilitating absorbance of aportion of the incidental reflected light. The third layer 44 may haveany thickness suitable to achieve the desired optical path lengthdifferential and to facilitate function of the pixel cell 10. Asdepicted, it is contemplated that the third layer 44 has a thickness Tranging between about 300 angstroms and about 8000 angstroms. In anon-limitative example, the third layer 44 has a thickness rangingbetween about 250 and about 1000 angstroms.

The third (standoff) layer 44 may be composed of materials havingsuitable optic qualities such as a refractive index between about 0.005and about 0.050 at the thickness T noted. Examples of suitable thirdlayer 44 materials include, but are not limited to, at least one ofsilicon dioxide, silicon nitride, silicon carbide, and air.

As depicted herein, it is contemplated that the light-absorbing layer 28may possess overall optical characteristics such as refractive index (n)and extinction coefficient (k), that are variably dependant on thewavelength of the light to be absorbed. It is contemplated that thelight-absorbing layer 28 may efficiently exhibit a refractive indexbetween 1.7 and 2.0 at a wavelength of 5500.

In an embodiment, the light-absorbing layer 28 may also include a fourthlayer 45 established on the second layer 42. The fourth layer 45 may beany suitable material or mixture of materials adapted to perform adesired function (e.g. anti-reflective coating). In a non-limitativeexample embodiment, the material is a transparent dielectric. Anysuitable transparent dielectric may be used, non-limitative examples ofwhich include magnesium fluoride, silicon dioxide, titanium dioxide,magnesium oxide, alumina, zirconium dioxide, yttrium oxide, bariumdifluoride, calcium difluoride, lead fluoride, thorium dioxide, chromiumoxide, hafnium dioxide, tin dioxide, zinc oxide, tantalum pentoxide,cadmium sulfide, zinc sulfide, and/or mixtures thereof. It is to beunderstood that the thickness of the fourth layer 45 ranges betweenabout 0 angstroms and about 30,000 angstroms. In one embodiment, thefourth layer 45 is about 600 angstroms.

It is to be understood that the fourth layer's 45 refractive index andoptical thickness may be selected such that the layer 45 acts as, forexample, an anti-reflective coating to substantially minimize surfacereflections. In an embodiment, the fourth layer 45 may include a gradedindex material(s) or film(s) such that it functions as ananti-reflective coating. In this embodiment, no additionalanti-reflective coated is used. The refractive index of fourth layer 45may vary throughout the layer 45 to substantially match the refractiveindex of air that may be present at an air/fourth layer 45 interface,thereby substantially reducing or eliminating surface reflections fromthe fourth layer 45. By gradually changing the refractive indexthroughout the layer 45, the abrupt optical interface between the layer45 and the air is substantially reduced or eliminated. Without beingbound to any theory, it is believed that reduction or elimination of theinterface substantially reduces or eliminates surface reflections, whichmay be detrimental to contrast of the system.

The fourth layer 45 may also include a series of layers and/or multiplelayers. This series of layers within layer 45 may include dielectriclayers that serve to cancel undesirable reflections from each other. Itis to be understood that this series of layers may act an asanti-reflective coating. The layer 45 may range between one to severaldozen individual film stacks (layers) depending, in part, on the degreeof complexity and functionality desired for the device 10.

In an embodiment in which the fourth layer 45 includes a series oflayers acting as an anti-reflective coating, the thickness andrefractive index of the layer(s) 45 may minimize reflections that mayoccur off of an optical interface between the second layer 42 and thefourth layer 45. It is to be understood that these undesirablereflections may degrade performance aspects of the light modulator,including, but not limited to color gamut and contrast. Non-limitativeexamples of materials that may be used in layer 45 to function as theanti-reflective coating include magnesium difluoride, titanium dioxide,silicon dioxide, magnesium oxide, alumina, zirconium dioxide, yttriumoxide, barium difluoride, calcium difluoride, lead fluoride, thoriumdioxide, chromium oxide, hafnium dioxide, tin dioxide, zinc oxide,tantalum pentoxide, cadmium sulfide, zinc sulfide, and/or mixturesthereof.

FIG. 2C depicts an alternate embodiment of the fourth layer 45, in whichan optional additional layer 47 is added to assist the fourth layer 45in functioning as an anti-reflective coating.

For illustrative purposes, FIG. 3 shows a top view of the pixel cell 10of FIG. 1 with the light-absorbing layer 28 over the second region 16including the clearout region 22 located in the center of the pixel 12.

It is to be understood that the light-absorbing layer 28 may bepositioned relative to the second region 16 in any manner that willfacilitate reduction in the reflection of unwanted light. Thus, thelight-absorbing layer 28 may contact (directly and/or indirectly)elements of the second region 16. By way of a non-limiting example, thedevice may include a passivation layer 46 disposed between the secondregion 16 and the light-absorbing layer 28 as shown in FIG. 4.

The passivation layer 46 may be selectively disposed on elements of thesecond 16 and may also be disposed on the first region 14. When thepassivation layer 46 is disposed on the first region 14, it iscontemplated that it will be composed of a material or materials that donot impede the performance of the first region 14. Thus, the materialmay possess suitable optical transparency as well as appropriatedielectric characteristics. Such materials are generally known to theskilled artisan.

When the passivation layer 46 is employed, it is contemplated that thelight-absorbing layer 28 may be directly disposed on the passivationlayer 46. Alternatively, a gap 29 may be formed between the passivationlayer 46 and the light-absorbing layer 28, such that the light-absorbinglayer 28 is suspended relative to the passivation layer 46 and theassociated second region 16.

In some example embodiments, the light-absorbing layer 28 may beemployed in a dual gap configuration. The dual-gap device 30 as depictedin FIG. 4 includes a passivation layer 46 disposed on the primary lightreflective region 14, and also interposed between the light-absorbinglayer 28 and the second region 16. As depicted, a gap 29 may be formedbetween the light-absorbing layer 28 and either the passivation layer 46or the elements of the second region 16.

The pixel cell 10 having light-absorbing layer 28 may be made by amethod that encompasses establishing a light-absorbing layer 28 inoverlying relationship to a second region 16 on a substrate 26. Thesubstrate 26 may have both a first region 14 and the second region 16disposed thereon. “Establishing” as used herein contemplates suitabledeposition and configuration or patterning steps.

Establishment of the light-absorbing layer 28 may include establishingat least two material layers in contact with the second region 16. In anembodiment, the second layer 42 has a reflectivity less than about 75%.The second layer 42 may be composed of a material that includes at leastone of tantalum aluminum alloys, tungsten silicon alloys, tantalumnitride alloys, nickel, nickel alloys, tantalum nitride alloys, andmixtures thereof.

To produce the embodiment as depicted in FIG. 2B, the first layer 40 maybe deposited by any suitable deposition technique. The third (standoff)layer 44 may then be deposited in contact with the first layer 40 by anysuitable deposition technique. This is followed by deposition of thesecond layer 42. Still further, the method may include depositing afourth (transparent dielectric) layer 45 on the second layer 42.Non-limitative examples of suitable deposition techniques includevarious additive processes including, but not limited to physical vapordeposition (PVD), chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), evaporation, sputtering, epitaxy, andthe like.

In some embodiments, the light-absorbing layer 28 may be constructed asa two-layer structure. In such embodiments, typically the two layerswill include the first layer 40 having a reflectivity characteristic andthe second layer 42 having a reflectivity less than about 75%.

In an example embodiment, the first layer 40 has a reflectivity greaterthan about 35%; while in an alternate embodiment, this reflectivityranges between about 85% and about 92%. In an example embodiment, thesecond layer 42 has a reflectivity ranging between about 10% and about25%; while in an alternate embodiment, this reflectivity ranges betweenabout 25% and about 50%. In a further example embodiment, thereflectivity of both the first and second layers 40, 42 is less thanabout 75%. Still further, a non-limitative example embodiment includesthe first layer 40 having a reflectivity ranging between about 40% andabout 50% and the second layer 42 having a reflectivity ranging betweenabout 15% and about 20%.

The fabrication methods as described herein may further includeestablishing a passivation layer 46 over the first region 14 and thesecond region 16. Establishment of the passivation layer 46 may occurprior to the establishment of the light-absorbing layer 28 (as depictedin FIG. 4) and may be accomplished by any suitable deposition processesand patterned as desired and/or required. This embodiment of the methodcontemplates direct contact between the passivation layer 46 and thelight-absorbing layer 28. As discussed herein, a gap 29 may optionallybe formed between the light-absorbing layer 28 and the passivation layer46. The gap 29 may be formed by any suitable fabrication method orsequence.

An example of a non-limiting fabrication method is illustrated in thebuild sequence set forth in FIGS. 5A through 5D.

As depicted in FIG. 5A, a substrate 26 having at least one first region14 and at least one second region 16 disposed thereon is provided.

A sacrificial layer 48 is established on at least a portion of the firstregion 14 (e.g. a pixel) and at least a portion of the second region 16.Establishment may be accomplished by suitable deposition and patterningtechniques. The sacrificial layer 48 may be composed of any materialsuitable for subsequent removal by appropriated post fabrication removaltechniques. Such removal techniques include, but are not limited to,various dry or wet etching methods (such as gas or vapor phase etching),physical etching by ion bombardment or plasma etching, and chemical orphysical/chemical etching. It is also contemplated that the sacrificialmaterial 48 of choice may be one amenable to wet etching methods orother subtractive processes. It is contemplated that suitablesacrificial layer 48 materials include, but are not limited to,compositions containing at least one of silicon, amorphous silicon,polysilicon, silicon nitride, silicon dioxide, and polyimide.

Referring now to FIG. 5B, the method further includes removing a portionof the sacrificial layer 48 from a region/area overlying a portion ofthe second region 16 thereby forming an exposed second region 16′. Theexposed second region 16′ may act as a supportive connector region forthe light-absorbing layer 28. By way of example, as illustrated in FIG.5B, the sacrificial layer 48 is removed from an area above an element ofthe second region 16, such as at post 18.

As depicted in FIG. 5C, after a portion of the sacrificial layer 48 isremoved, the method further includes establishing the light-absorbinglayer 28 on both the exposed second region 16′ and on a remainingportion of the sacrificial layer 48 which lies over the second region16. This results in a portion of the light-absorbing layer 28 beingdirectly in contact with the exposed second region 16′ (such as theregion defined by post 18) and a second portion of the light-absorbinglayer 28 being in contact with the remaining portion of the sacrificialmaterial 48.

The method includes removing the remaining portion of the sacrificialmaterial 48, as depicted in FIG. 5D. Removal may be accomplished by anysuitable method. Space(s) 50 are created between portions of thelight-absorbing layer 28 and portions of the second region 16 after theremaining portion of the sacrificial material 48 is removed. Asdepicted, at least one portion of the light-absorbing layer 28 isdirectly in contact with a portion of the second region 16, such as atpost 18 or other suitable support structure(s). The second portion ofthe light-absorbing layer 28 may be suspended relative to other elementsof the second region 16, for example the flexure(s) 24 and the clearoutregion(s) 22, thereby defining space(s) 50 therebetween to yield adevice which may be referred to as a single gap device 60.

During fabrication of the single gap device 60, the second region 16 hasat least one supportive connector region (such as post 18) and at leastone underlying region (such as flexure 24) covered by a sacrificiallayer 48 that is interposed between the flexure 24 (or other element ofthe second region 16) and the light-absorbing layer 28. The sacrificiallayer 48 is ultimately removed (e.g. etched away) such that thelight-absorbing layer 28 is directly in contact with the post 18 and issuspended relative to the flexure 24.

The light-absorbing layer 28 may be utilized in various systemsincluding, but not limited to front and rear projectors, near eyedevices, direct view displays, and integrated circuits. A non-limitativeexample of a display device is depicted in FIG. 6. It is contemplatedthat the display device 70 may include at least one pixel cell arrayconfigured with the light-absorbing layer 28 disclosed herein. Asdepicted in FIG. 6, light from light source 72 is focused on a lightmodulating device 84 (such as pixel cell 10) by lens 74. Although shownas a single lens, 74 is typically a group of lenses, integrators, andmirrors that together focus and direct light from light source 72 ontothe surface of the pixel cell 10. Image data and control signals fromcontroller 76 are written onto a suitable SRAM cell, DRAM cell,capacitor, or other memory element associated with each pixel cell 10,including the pixel itself or a pixel cell array in the light modulationdevice 84. The data in these associated cells may cause at least onepixel to actuate to the light modulating or “on” state. Pixel cells 10that are in the unactivated or off state can reflect light away fromprojection lens 80 and optionally into a light trap 78. Alternatively,pixels in the on state can absorb light in a different portion of thevisible spectrum than pixels in the off state, thus providing lightmodulation. In one embodiment, multiple pixel states with multipleabsorbing characteristics may be employed. While multiple pixel cells 10may be actuated to an “on” state to reflect light to projection lens 80,a single lens is shown for simplicity. Projection lens 80 focuses thelight modulated by the light modulation device 84 onto a single imageplane or screen 82.

At least a portion of light reflected off the regions 16 of the pixelcell 10 array of the spatial light modulating device 84 is absorbed by alight-absorbing layer 28 associated with the pixel cell 10 array and isprevented from reaching the projection lens 80 and/or single image plane82.

Embodiments of the light-absorbing layer 28 may be used in a variety ofapplications. For example, the light-absorbing layer may beadvantageously included in various projectors and integrated circuitarchitectures utilizing various light reflecting or light emittingdevices.

In some embodiments, the integrated circuit will include a semiconductorsubstrate 26 as well as a first region 14 disposed on the semiconductorsubstrate 26. A second region 16 (typically composed of supportstructures not configured for light reflection and fabricationartifacts) is also disposed on the semiconductor substrate 26. Alight-absorbing layer 28 may be in contact with at least a portion ofthe second region 16. It is contemplated that an integrated circuit suchas one employing a pixel cell 10 having the light-absorbing layer 28thereon may be used as a single wavelength tool if desired and/orrequired. For example, the integrated circuit having the light-absorbinglayer 28 disposed thereon may be tunable to a wavelength (anon-limitative example of which includes 190 nm) to obtain low lightreflectance at a specific range from the incidental light reflectiveregion 16.

To further illustrate the light-absorbing layer 28 and light modulatingdevice 84 disclosed herein, reference is made to the following examples.The following examples are for illustrative purposes and are notintended to limit the scope of the present disclosure or embodiments asclaimed.

EXAMPLE 1

In order to evaluate the effectiveness of light-absorbing layers 28 inlight modulation devices, a test device having pixel cells with firstregions and second regions was fabricated having the generalconfiguration as shown in FIG. 1.

A sacrificial layer was deposited over the first region and secondregion. A light-absorbing layer was formed over the second region (andon the sacrificial layer) by first depositing a first layer including800 angstroms of aluminum. Then, a standoff (third) layer including 500angstroms of silicon dioxide was deposited on the aluminum. Thelight-absorbing layer was completed by depositing a second layerincluding 75 angstroms of tantalum aluminum on the silicon dioxide.

The resulting device was evaluated according to various parameters andfound to be functional with reduced reflections from the incidentallight reflective regions.

EXAMPLES 2-4

Optical simulation results of the reflectance of various light-absorbinglayers in which the thickness of the silicon dioxide layer (standoff(third) layer) of the light-absorbing layer was altered to 600, 700, and800 angstroms, respectively, (as described in Examples 1 through 4) aredepicted in FIG. 7.

The graph of FIG. 7 shows the percent reflectivity versus the incidentalwavelength. As shown in FIG. 7, the reflectance of the light-absorbinglayer averages about 4% across the visible spectrum with a standofflayer thickness of 600 angstroms of silicon dioxide (described inExample 2). The aluminum layers in examples 1-4 were found to have areflectivity of about 92%, while the tantalum aluminum layers have areflectivity of about 18%. As shown in FIG. 7, the reflectance of lightfrom the second region was reduced when the light-absorbing layers werepresent.

EXAMPLE 5

A calculation of the reflectance of the pixel cell in its dark state,both with and without the light-absorbing layer, was performed. Thereflectance of one pixel cell having a light-absorbing layer including afirst layer of 800 angstroms of aluminum, a standoff (third) layer of600 angstroms of silicon dioxide, and a second layer of 75 angstroms oftantalum aluminum was compared to the reflectance of a similar pixelcell in which the light-absorbing layer was omitted.

Total reflectance of the first region and the second region for thepixel prepared without the light-absorbing layer was calculated. Theresults are shown in Table 1.

The results indicate that without the light-absorbing layer, the totalreflectance of the entire pixel cell is about 15% due in part to thereflection from the second region. The light from this region dominatesthe percentage of the total reflected light, thus generally degradingthe color gamut and contrast of the total system. TABLE 1 % Area ofPixel Cell Regions & Contribution to Reflected Light WithoutLight-absorbing Layer (HID Layer) % Total % Total % Input LightReflected Region Squares % Area Reflectance Reflected Light Bottom 8248.16% 92.0% 7.51% 48.0% Capacitor Plate Area Flexure & 973 9.64% 46.0%4.43% 28.3% Post Area Clearout 49 0.49% 92.0% 0.45% 2.9% Pixel Area 825081.72% 4.0% 3.27% 20.9% Total 10096 100.00% 15.66% 23.7%

The total reflectance of the second region of the pixel cell with thelight-absorbing layer thereon and the total reflectance of thecorresponding first region was calculated and is collected in Table 2.While the total reflectance of the pixel remains at about 4%, the amountof reflected light is now dominated by the first region (the pixel)rather than by the second region (the bottom capacitor plate area,flexures, posts, and clearout regions). A slight reduction in thepercent of active area (first region) from 81.7% to 76.7% was noted.TABLE 2 % Area of Pixel Cell Regions & Contribution to Reflected LightWith Light-absorbing Layer (HID Layer) % Total % Input % TotalReflectance Light Reflected Region Squares % Area (With HID) ReflectedLight HID Area 2566 23.31% 4.0% 0.93% 23.3% Pixel Area 8444 76.69% 4.0%3.07% 76.7% Total 11010 100.00% 4.00% 100.00% 

Hence, in some embodiments, the dark state reflection of the firstregion and second region may be reduced with the utilization of thelight-absorbing layer over the second region. The light-absorbing layerof aluminum, silicon dioxide, and tantalum aluminum has about 4%reflectivity as opposed to the about 9% reflectivity of alight-absorbing layer including aluminum, silicon dioxide, and titaniumnitride. The lower reflectivity may result in higher contrast for someembodiments.

While several embodiments have been described in detail, it will beapparent to those skilled in the art that the disclosed embodiments maybe modified. Therefore, the foregoing description is to be consideredexemplary rather than limiting.

1. A method of making a spatial light modulator, comprising: providing afirst region capable of light generation by modulation and a secondregion coupled thereto; establishing a sacrificial layer overlying atleast a portion of the first region and the second region; removing aportion of the sacrificial layer from an area over the second region,thereby forming an exposed second region; establishing a light-absorbinglayer on the exposed second region and on a remaining portion of thesacrificial layer overlying the second region, whereby a portion of thelight-absorbing layer is in contact with the exposed second region, anda second portion of the light-absorbing layer is in contact with theremaining portion of the sacrificial layer and is suspended relative tothe second region; and removing the remaining portion of the sacrificiallayer.
 2. The method as defined in claim 1 wherein establishing thelight-absorbing layer further comprises: establishing a first layerhaving a reflectivity characteristic; and establishing a second layerconnected to the first layer, the second layer having a reflectivityless than about 75%.
 3. The method as defined in claim 2 wherein thefirst layer has a reflectivity greater than about 75%.
 4. The method asdefined in claim 2 wherein establishing the light-absorbing layerfurther comprises: establishing a standoff layer between the first andsecond layers; and establishing a transparent dielectric layer connectedto the second layer.
 5. The method as defined in claim 4 wherein thetransparent dielectric layer is adapted to function as ananti-reflective coating.
 6. The method as defined in claim 1 wherein thefirst region is a primary light reflective region, and the second regionis an incidental light reflective region.
 7. The method as defined inclaim 1 wherein establishing the light-absorbing layer furthercomprises: establishing a first layer having a reflectivity less thanabout 75%; and establishing a tantalum aluminum layer connected to thefirst layer.
 8. The method as defined in claim 7 wherein thelight-absorbing layer further comprises a third layer interposed betweenthe first layer and the tantalum aluminum layer.
 9. The method asdefined in claim 8 wherein the third layer is a standoff layer that hasan optical transparency and a thickness so as to absorb at least aportion of the light.
 10. A method of making a spatial light modulator,comprising the steps of: providing a substrate, the substrate having afirst region and a second region disposed thereon, wherein the firstregion comprises a pixel, and wherein the second region comprises atleast one post and at least one flexure; depositing a sacrificial layerover the pixel, the at least one flexure, and the at least one post;removing a portion of the sacrificial layer disposed on the at least onepost, thereby forming a supportive connector region for alight-absorbing layer; depositing a light-absorbing layer on thesupportive connector region and on the sacrificial layer disposed on theat least one flexure; and etching a portion of the sacrificial layerdisposed on the at least one flexure, whereby a portion of thelight-absorbing layer is connected to the at least one post, and asecond portion of the light-absorbing layer is suspended relative to theat least one flexure.
 11. An integrated circuit, comprising: asemiconductor substrate; a first region disposed on a first portion ofthe semiconductor substrate; a second region disposed on a secondportion of the semiconductor substrate; a passivation layer disposed onthe first region and the second region; and a light-absorbing layerdisposed on the passivation layer and contacting at least a portion ofthe second region, the light-absorbing layer including: a first layer;and a second layer connected to the first layer, the second layer havinga reflectivity less than about 75%.
 12. An integrated circuit,comprising: a semiconductor substrate; a first region disposed on thesemiconductor substrate; a second region disposed on the semiconductorsubstrate; and a light-absorbing layer suspended relative to the secondregion.
 13. The integrated circuit as defined in claim 12 wherein thesecond region comprises at least one post and at least one flexure. 14.The integrated circuit as defined in claim 12 wherein thelight-absorbing layer is in contact with the at least one post and issuspended in indirect contact with the at least one flexure.
 15. Theintegrated circuit as defined in claim 12 wherein the light-absorbinglayer includes: a reflective first layer having a reflectivity greaterthan about 75%; and a second layer connected to the reflective firstlayer, the second layer having a reflectivity less than about 75%. 16.The integrated circuit as defined in claim 12 wherein the first regionis a primary light reflective region, and the second region is anincidental light reflective region.
 17. The integrated circuit asdefined in claim 15 wherein the second layer comprises at least one oftantalum aluminum alloys, tungsten silicon nitride alloys, tantalumnitride alloys, nickel, nickel alloys, titanium nitride alloys, andmixtures thereof.
 18. The integrated circuit as defined in claim 15wherein the second layer comprises tantalum aluminum.
 19. The integratedcircuit as defined in claim 15 wherein the second layer is capable ofabsorbing at least a portion of directed light having a wavelengthbetween 400 and 700 nanometers.